The physiology, microcirculation and clinical application of the shunt-restricted arterialized venous flaps for the reconstruction of digital defects

Abstract

Reconstruction of digital defects using the venous flap offer several advantages but remained unpopular owing to levels of venous congestion rates. We performed animal studies to test the hypothesis that an arterio-venous shunt increases pressure for peripheral flap perfusion and decreases venous congestion. Using an abdominal adipofascial flap model in six male Sprague-Dawley rats, microcirculation was modified as follows: type I - arterial flap; type II - flow-through arterio-venous flap (AVF); and type III - shunt-restricted AVF. In type I flaps, blood flow was observed to be unidirectional in both arterioles and venules. In type I flaps, blood flow was observed to be unidirectional in both arterioles and venules. In type II flaps, blood flow oscillated without a dominant direction and came to a standstill. In type III flaps, blood flowed proximally in a reverse direction whereas distally, flow was similar to type I flaps. In a clinical series, 21 patients received a total of 22 shunt-restricted AVFs. All 22 clinical flaps survived; four flaps suffered epidermolysis but recovered without full thickness loss.

The position of ‘shunt restriction’ along an arterialized vein affects venous congestion and flap perfusion of an arterialized venous flap

“…6,7 This finding was similar to the observations reported by Suzuki. 11 Unlike the flow-through venous flaps, in which arterial blood traverses the flaps without providing peripheral perfusion, 2 'shunt restriction' improves peripheral circulation by rerouting the direction of blood flow towards the rest of the flap.…”

“…In our prior study, 7 we postulated that blood flow from non-physiological perfusion in the proximal flap was obstructed by blood that was already in the arteriole. The blood in the arteriole originated from the more proximal arteriovenous shunt and created a pressure gradient from the proximal to distal direction.…”

“…We previously placed 'shunt restriction' at the midpoint of the AV shunt, but mild to moderate venous congestion remained inevitable in AVFs with an I-pattern venous network. 6,7 The vessel network has been described according to the pattern observed within the flap. We have observed previously that intra-flap vessels can take an 'I'-or 'H'-pattern type of vessel network.…”

“…6,7 The postoperative appearance of 'shuntrestricted' venous flaps is similar to regular arterial flaps and can be monitored without confusion. In our series, the worst outcome was partial loss with epidermolysis of the skin flap.…”

“…6,7 In this technique, the venous flap is first arterialized along the direction of the valves. A haemoclip is then applied at a location between the arterialized vein and drainage vein, that is, 'shunt restriction'.…”